Ancient genes persist

Stone Age interbreeding with Neandertals appears to have left its mark in humans’ genes. In “Neandertal hot spots highlighted in modern humans’ DNA” (SN: 3/8/14, p. 12), Bruce Bower reported that variants in genes relating to skin and hair traits, as well as some autoimmune disorders, come courtesy of these ancient hominids.

“I found your article fascinating, especially following my recent reading of Svante Pääbo’s book on the topic (Neanderthal Man: In Search of Lost Genomes, reviewed in the same issue),” reader Sala Horowitz wrote in an e-mail. “I can surmise why a skin genome legacy from our cousins might have proved useful in human evolution, perhaps to more efficiently synthesize vitamin D from sunlight, but why would a genetic inheritance for autoimmune diseases not have been selected against?”

It’s a good question, says Bower, and one that scientists haven’t answered definitively.

A genetic mutation (indicated in blue) causes sickle-cell anemia. But people who inherit only one copy of the mutated gene receive some protection against malaria. Similar unexpected benefits may be the reason some other genetic disorders stick around in the population. Source: CDC

“Perhaps genes involved in lupus and a few other autoimmune conditions were also involved in other, beneficial processes. This appears to be the case with sickle-cell anemia (see left): The mutation that causes the disorder warps the shape of oxygen-carrying proteins in red blood cells, but it also produces compounds that protect against malaria in individuals who carry just one mutated copy of the gene and don’t have the disease. Whether genetic variants associated with autoimmune disorders offer advantages of their own is, as the scientists like to say, a matter for further research.”

Reactions to a fusion milestone

In “Step taken toward ignition” (SN: 3/8/14, p. 6), physics writer Andrew Grant announced that the National Ignition Facility recently achieved fusion reactions that briefly sustained themselves. The results represent progress in the quest to achieve ignition, a crucial first step in producing usable energy from fusion reactions.

Some readers responded optimistically to the news. “I visited the Princeton stellarator while I was in high school in 1960 or 1961,” commentedTom on the Science News website. “Surprise, I’m still a believer. It is one of the main energy sources of the universe and it’s the civilized power source. I’d like to see it happen in my lifetime, but I’d accept waiting until my grandchildren could enjoy it when they’re my age.”

Others, though, were more reserved with their enthusiasm. “It seems fusion is always 20 years away from scientists handing it off to engineers,” Jan Steinman said. Commenter VietVetBob agreed: “I’ve been watching this science for 40-plus years now, and as Jan said, it always seems 20 years away. I’ve been waiting a long time for that free energy bill.”

Bacteria for better energy

In “Spore power” (SN: 3/8/14, p. 4), chemistry writer Beth Mole described the science behind a new generator that harnesses mechanical energy from swelling and shrinking Bacillus spores to produce an electric current.

“In a practical arrangement, wouldn’t the spores either quickly rot or become contaminated? They must need some other nutrients to stay alive,” wrote Mark S. in the online comments. “Would the surface need to be constantly recoated with new spores?”

The spores are actually incredibly hardy, says Mole, because they’re metabolically dormant. “They’re not processing nutrients, so they don’t need any rations. They can survive harsh conditions, such as extreme temperatures and dryness, and they have little risk of rotting. Though the researchers aren’t sure exactly how long the spores could last, they have the potential to be stable on the power-generating device for long periods of time — possibly years.”

As for contamination, Mole notes, “the researchers say the spore-covered device is no more likely to become polluted than any other type of machinery. They intend to test this in the long run and expect that, if needed, common chemical treatments could help keep the spores spotless.”

More Stories from Science News on Genetics